title: Pretreatment with small-dose ketamine reduces predicted effect-site concentration of propofol required for loss of consciousness and Laryngeal Mask Airway insertion in women.
abstract: OBJECTIVE
  To investigate the effect of small-dose ketamine on the predicted effect-site concentration of propofol required for loss of consciousness (LOC) and Laryngeal Mask Airway (LMA) insertion.
  
  
  METHODS
  Randomized, double-blinded study.
  
  
  METHODS
  Operating room.
  
  
  METHODS
  50 ASA physical status 1 and 2 women scheduled for elective breast or gynecological surgery.
  
  
  METHODS
  Patients were randomly allocated to a ketamine group or a control group. Thirty seconds before propofol injection, ketamine group patients received ketamine 0.2 mg/kg, while control group patients received saline. Propofol was given in a target-controlled infusion and target blood concentration was gradually increased until LOC. The effect-site concentrations for attempting LMA insertion was predetermined by modifying Dixon's up and down method. LMA insertion was attempted without muscular blocking agents.
  
  
  METHODS
  Pain scores on propofol injection, effect-site concentrations at LOC, hemodynamic variables, and patient movement or side effects on LMA insertion were recorded.
  
  
  RESULTS
  The effect-site concentration of propofol required for LOC was 2.14 μg/mL for the control group and 1.66 for the ketamine group (P = 0.0082). The predicted effect-site concentration of propofol alone at which 50% of patients did not move with LMA insertion (EC(50)LMI) was 3.59 μg/mL (95% CI: 3.18 ∼ 4.19 μg/mL). Pretreatment with ketamine 0.2 mg/kg decreased EC(50)LMI from 3.59 (3.18 ∼ 4.19) to 2.39 (1.22 ∼ 2.99).
  
  
  CONCLUSIONS
  Pretreatment with ketamine 0.2 mg/kg reduced the propofol concentration required for both LOC (22%) and LMA insertion (33%) in women.
authors.affiliation: Department of Anesthesiology, Ibaraki Children's Hospital and Mito Saiseikai General Hospital, Futabadai 3-3-1, Mito City, Ibaraki 311-4145, Japan. okuoku-yo@est.hi-ho.ne.jp
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Okuyama
authors.forename: Shinichi
authors.initials: S
authors.lastname: Inomata
authors.forename: Naomitsu
authors.initials: N
authors.lastname: Okubo
authors.forename: Iwao
authors.initials: I
authors.lastname: Watanabe
mesh_terms: D000328:Adult; D000368:Aged; D000778:Anesthetics, Dissociative / Q000008:administration & dosage / Q000627:therapeutic use*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001943:Breast Neoplasms / Q000601:surgery; D004311:Double-Blind Method; D005260:Female; D013509:Gynecologic Surgical Procedures / Q000379:methods; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage / Q000627:therapeutic use*; D017214:Laryngeal Masks; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D000778:Anesthetics, Dissociative; D018686:Anesthetics, Intravenous; D007649:Ketamine; D015742:Propofol